A new study from Rutgers University in New Jersey shows food is instantly contaminated with bacteria the minute it hits the floor.

But Aston University microbiology professor Anthony Hilton says there is more to the story than simply how many bacteria are transferred on impact.

His initial study into the dropped food effect in 2014 found that certain food left for three seconds could contain up to ten times fewer bacteria than food left for 30 seconds — revealing that time is an important factor.

Prof Hilton and his team have now carried out an experiment for The Sun — dropping cooked pasta, midget gem sweets, biscuits and toast on laminate flooring and carpets for three seconds and 30 seconds and measuring the bacteria.

Prof Hilton explains: “In surveys of people’s homes, the predominant bacteria found on both flooring types were mostly harmless human skin bacteria and some environmental ones found in soil and dust — certainly not the harmful bacteria people worry about. Put simply, many of the same bacteria you would be putting in your mouth if you licked your own fingers after eating a doughnut. They’re bacteria we live alongside comfortably.”

He adds that exercising common sense and is important in knowing whether to eat dropped food.

Don’t eat food dropped outside

He says: “No one should be picking food up and eating it from anywhere outside, be it the park, train station or shopping mall. Similarly, if you have pets — especially cats and dogs or outdoor pets — you shouldn’t be picking food off the floor at home to eat because you don’t know which bacteria your outdoor pets have exposed themselves to and could be bringing home.

“But if you’re confident you have a hygienically clean home where you vacuum carpets once or twice a week, use detergent on hard floors once a week and take outdoor shoes off when you’re entering, the likelihood is you won’t expose yourself to any more bacteria than is already on your body by picking up a piece of toast which has just dropped on the floor and eating it.

“There are far greater infection hazards in the home to worry about, such as Campylobacter, on poultry. So whether it’s the three-second rule, five-second rule or blowing it, what matters most where dropped food is concerned is to exercise common sense.

“Anyone who has had children will know toddlers drop the same piece of breakfast toast several times before they finally finish it. In our lab experiments we deliberately seeded the floor surfaces with more than 17million bacteria. Some foods only picked up 50 of those 17million bacteria.

“In real life we have never seen anything like this starting level of harmful bacteria on indoor flooring so the risks involved in picking up a dropped biscuit, crisp or piece of toast from the floor in your home and eating it are minimal.”